The tread belt pneumatic tires which are the subject of the method of the present invention are very large tires (greater than 120 inch outside diameter (OD)) generally designed for use on very large vehicles, generally off-the-road (OTR) vehicles such as earthmovers and large-capacity mining trucks (e.g., 300 short tons or more). These very large tires and vehicles are generally utilized at long-term mining or construction sites such as rock quarries, mines, foundries, major tunnel/roadway construction, dams/dikes, and the like. The very large vehicles are generally too large to transport to the work site normally, and are therefore often shipped in pieces to the work site where the pieces are assembled/welded together for use. As modern construction vehicles have evolved to larger and larger sizes, their tires have also grown to the point where conventional shipping of the tires becomes difficult. For example, an existing design of 360 ton (32,6530 kg) truck requires pneumatic tires of 150 to 154 inch diameter (3.91 meter) which is considered to be the maximum size tire reasonably possible to ship by conventional rail or roadway means in the United States. Tire weight is another consideration, as very large tires can weigh 8,000 pounds (3,628 kg) to 15,000 pounds (6,803 kg) or more per un-mounted tire. The industry would like to progress to even larger, 400 ton (362,812 kg) or 450 ton (408,163 kg) trucks with correspondingly larger tires of 160 inch (4.07 meter) diameters or more. Depending on local limitations of shipping means (such as tunnel/bridge clearances and roadway weight limits), even somewhat smaller ones of the "very large tires" may pose significant problems, and may therefore require extraordinary transport means such as by helicopter.
Another problem faced by the users of very large pneumatic tires is changing the very large tires on the very large vehicles. The very large vehicles are generally employed in areas such as rock quarries, where the tires are subjected to high stress and loads, usually under harsh environmental conditions wherein tires are subjected to puncture-producing and wear-inducing conditions. Under these conditions, tires are damaged relatively frequently and must be changed at the work site. Even with removable-flange wheels, changing very large tires is a difficult and time-consuming process, requiring as much as 5 to 6 hours for a single tire change.
Another problem is storage of the very large tires at the work site. As tires become larger, more and more space is required for storage. Also, if operating conditions are particularly harsh, or if shipping of replacement tires "on demand" is not practical, then increased numbers of spares must be stocked, further increasing the storage space needed. Furthermore, some job sites require different tread designs for different operating conditions. For example, wide treads with deep cleats may be needed for muddy conditions such as in rainy weather, versus normal-width treads with a different cleat design for operation on gravel or in dry weather conditions. Given the time consuming nature of the existing tire-changing methods, changing tires to obtain optimum tread patterns is not always feasible.
Finally, even if driving tires and steering tires on the very large vehicles are the same overall size, the tread patterns of the two types of tires need to be different for most effective operation. This again adds to the number of replacement tires which must be stored at a work site.
There is therefore a need for a method of shipping very large tires that allows for the employment of more conventional shipping means, and there is a desire to reduce the work site storage requirements as well as to improve the efficiency of the very large tire changing process.
Although tires having replaceable treads are known in automotive/motorcycle and conventional truck tire applications, it is not until recently that tread belt tires have been developed to meet the unique requirements of very large pneumatic tires for very large vehicles. U.S. patent application Ser. No. 09/424,089 entitled TIRE WITH IMPROVED REMOVEABLE TIRE TREAD BELT to Rayman, having a common assignee with the present invention, of which this invention is a continuation in part, discloses a tire with an improved removable tire tread belt for use on large earthmover vehicles. This tread belt tire (also called a "track belt tire") "is constructed of a removable tread belt assembly mounted to the outer circumferential surface of an inflatable tire carcass. A unique track belt design restrains the track from expanding while simultaneously improving the secure mounting of the track to the carcass and providing improved penetration protection. Also, the improved track belt will maintain a flatter tread profile which in turn will improve tread life and durability."
A predecessor version of removable treads or tracks for very large tires is discussed in U.S. Pat. No. 4,351,380, wherein certain prior art track belt tire assemblies comprise a plurality of ground-engaging "shoes" spaced about the periphery of the supporting structure. The heavy loads on the "shoes" result in great stresses being developed that sometimes lead to premature tire failure. The U.S. Pat. No. 4,351,380 patent is directed to an improved track belt assembly which comprises a plurality of shoes spaced about the periphery of a load-supporting structure and secured to a reinforcing belt structure disposed on the side of the shoe opposite the ground-engaging side thereof.
A body of prior art exists for tires with removable tread belts (see, for example, U.S. Pat. Nos. 3,897,814; 3,224,482; 3,087,526; and British Patent G.B. 2,073,109). However these patents were directed toward the addressing of various issues related to tires used by predominantly roadway vehicles such as automobiles and trucks. Examples of these issues include: varying cord spacing to reduce wear of the outer tread belt edge for "enhanced service life and lower manufacturing cost"; improving transverse bending for "better riding comfort and improved road holding ability"; and linking separate tread rings to improve "road-holding capabilities and . . . silent riding." Accordingly, the prior art has varied the quantity, shape, placement and spacing of tread rings, reinforcing belts, inextensible cords, and interlocking grooves in the tire carcass and tread belt, but these variations have not been adequate to address the special needs of off-the-road vehicle tires, nor of very large tires in general.
There are still unsolved problems, relating to a pneumatic tire and tread belt assembly, concerning shipping, storage, inventory, and changing of very large tires on very large vehicles.